104 Upload Resumption Supported

Temporary registration: interim response announcing that the server supports resumable uploads for this request.

104 at a glance

Code: 104
Name: Upload Resumption Supported (IANA: Upload Resumption Supported (TEMPORARY - registered 2024-11-13, extension registered 2025-09-15, expires 2026-11-13))
Class: 1xx Informational
Status: Temporary IANA registration
Defined in: draft-ietf-httpbis-resumable-upload-05
Cacheable by default: No. Interim (1xx) responses are never stored by caches.

What 104 means

104 Upload Resumption Supported comes from the IETF resumable uploads draft (draft-ietf-httpbis-resumable-upload). When a client starts an upload, the server can send 104 with the URL of an upload resource; if the connection drops, the client asks that URL how many bytes arrived and continues from there instead of starting over. The IANA registration is temporary and listed as expiring on 2026-11-13, so treat the code as experimental until the draft is published as an RFC.

What typically causes a 104

Servers and clients implementing the IETF resumable upload draft (it evolved from the tus protocol).
Apple platforms (URLSession) and some upload services have shipped draft support.

Fix it on the server

Only send it to clients that indicate support for the draft; unaware clients will ignore it as an unknown 1xx.
Track the draft version in your implementation, since header names changed between drafts.

Fix it as a client or visitor

If your client does not support the draft it should simply ignore the 104 and wait for the final status.

Headers that go with 104

Header	Role
`Location`	URL of the upload resource the client can use to resume.
`Upload-Draft-Interop-Version`	Draft revision both sides speak (named this way in recent drafts).

Example response

HTTP/1.1 104 Upload Resumption Supported
Upload-Draft-Interop-Version: 6
Location: https://example.com/upload/b530ce8ff

HTTP/1.1 201 Created